TRANS SLIPPING PLEASE HELP.....

Buick Electra

I have a 1985 buick electra park ave. With a 3.8l v6 4 speed auto. With roughly 200,000. The trans will take of in all gears, but when it trys to shift auto it goes out of gear, till it gets the rpms down. Have replaced trans modulator and all vacuum hoses, egr vacuum solinoid, tested the v.S.S and it was just fine I am lost please help! : Idea: : idea: : idea: : ( : ( : shock: : D

Thank you for your help the trans fluid level was fine, so I took it to the shop to get a used one in its is alot cheaper. With putting an old one in should the fluid and filter be changed plus new o-rings put in. Thanks you again for your help. : D : D : D : D : lol: